After his death at 84, Gifford became the oldest ex-NFL star diagnosed with the crippling disease linked to multiple concussions and severe head trauma. He played in the NFL for 12 years, all with the Giants.

Gifford, who retired in 1964, famously missed an entire season after a brutal tackle from Philadelphia Eagles linebacker Chuck Bednarik left him unconscious on the field in 1960.

Frank Gifford, who died in August, was diagnosed with CTE, which is linked to multiple concussions and brain injuries.

Though the family provided no details, Gifford reportedly suffered short-term memory loss in his later years. Other CTE symptoms include depression, dementia, anxiety and suicidal tendencies.

“We as a family made the difficult decision to have his brain studied in hopes of contributing to the advancement of medical research concerning the link between football and traumatic brain injury,” said the Gifford family statement.

The disease can only be diagnosed after death and only if relatives agree to allow testing. Gifford’s family said he died of natural causes.

Former players and health advocates have ripped the league in the past for a failure to prevent head injuries. The NFL, in a 2013 settlement, agreed to pay $765 million to settle concussion-related lawsuits from its retirees.

Frank Gifford, a Hall of Famer, last played in the NFL in 1964.

Gifford was among the league’s most popular players as football moved onto the national stage in the 1950s. His Giants were on the losing end of the “Greatest Game Ever Played” to the Baltimore Colts for the NFL championship in 1958.

Jennifer Smith, director of player outreach for Pain Alternatives, Solutions and Treatment, said news of the positive test wasn’t completely unexpected.

“If you played football as long as Frank Gifford, there is a probability you will suffer from CTE,” said Smith, whose organization has treated dozens of ex-NFLers for issues linked to traumatic brain injury. “This doesn’t surprise me.”

Other pro football stars diagnosed with the disease were from later NFL generations, including Hall of Famer Junior Seau, Pittsburgh Steelers center Mike Webster and one-time NFL man of the year Dave Duerson.

San Diego Chargers star Seau and Duerson, who played on the 1990 New York Giants Super Bowl champs, both committed suicide.

The addition of Gifford to the sad litany of post-career suffering could help alter the way America views its most popular sport, said attorney Michael Kaplen, who represents the Brain Injury Association of America.

Frank Gifford is carried off the field after a brutal hit from Eagles player Chuck Bednarik in 1960. Gifford was knocked unconscious and forced to miss an entire season.

(Kidwiler Collection/Diamond Images/Getty Images)

“Will it cause a sea change?” asked Kaplen. “It’s certainly a wave, and the tsunami is building. Players have to ask, ‘Is the money I might make from this game worth it?’ ”

The movie “Concussion,” starring Will Smith and opening on Christmas Day, details the history of CTE and the NFL.

NFL Commissioner Roger Goodell weighed in late Wednesday.

“We appreciate the Gifford family's desire to help the medical community understand more about CTE, and we are grateful for their support of the league’s efforts to improve safety in our game,” he said in a statement.

Giants hero Frank Gifford and wife Kathy Lee Gifford.

(Handschuh, David)

Frank Gifford had a successful career with "Monday Night Football." He's seen here with Al Michaels (c.) and Dan Dierdorf (r.).

(GREG HEISLER/ABC)

“At the NFL, we are supporting grants to (the National Institutes of Health) and Boston University as well as other independent efforts to research the effects of repetitive head trauma,” he said. “But we are not waiting until science provides all of the answers. We are working now to improve the safety of our game. The NFL has made numerous rules changes to the game, all to enhance player health and safety at all levels of football. These include 39 rule changes and better training and practice protocols that are yielding measurable results.”

The Giants issued a statement backing the Gifford family.

“We have great respect and sympathy for the Gifford family,” the team said. “We all miss Frank dearly. We support the family’s decision to contribute to the discussion and research of an issue we take very seriously.”

Gifford was MVP of the league in 1956, and was inducted into the Hall of Fame in 1977. He starred for the Giants as a halfback, wide receiver and defensive back during his long career.

The beloved athlete remained a frequent presence in the Giants organization through the decades and was always warmly received by the team’s rabid fan base.

He transitioned easily to the TV airwaves, becoming a regular calling “Monday Night Football” with Howard Cosell and Don Meredith.

The glib Gifford became one of the sport’s most recognizable talking heads, and handled some Olympic broadcasting chores while with ABC Sports.